1. Field of the Invention
The present invention relates to electrode balloons for picking up bioelectrical signals from the cavities of the heart for their simultaneous recording in a multitude of sites followed by the mapping of the endocardial activation potentials. More particularly, the present invention relates to an electrode balloon having a structure which is easily adaptable to any one of the cardiac chambers and which can be used in the right or left ventricles of the heart without resorting to a ventriculotomy.
2. Description of the Prior Art
There exists many types of electrode systems for recording endocardial activation potentials. Before the advent of simultaneous recording in a multitude of sites, the bioelectrical signals were taken from one site at a time using a hand-held probe. A long sequence of regular heartbeats or of constant morphology was necessary in order to have time to cover all the necessary sites required for making such a mapping.
Although it is still used occasionally, the hand-held probe has been replaced by devices carrying a multitude of electrodes which require two or three heartbeats for the mapping. Amongst these systems, we find endocardial balloons with spherical balls or plaquettes having a high density of electrodes thereon. The former permits a global view, for instance, of the endocardium of the left ventricle, while the latter provides in a more limited region thereof a multitude of lectures in very near sites. Such a concentration enhances the resolution and permits the grasping of very fine electrophysiological mechanisms. There also exists needles carrying a series of aligned electrodes that are inserted through the cardiac muscles in order to pick up signals from the endocardium.
U.S. Pat. No. 4,699,147 (issued on Oct. 13, 1987 to Chilson et al.) discloses a probe provided with a plurality of electrodes for intraventricular cardiac mapping. The probe comprises a catheter and four elongated wire assemblies received therein. Each wire assembly comprises a tubing, six insulated wire conductors received in the tubing, and a central core wire which is stiff but yet flexible. A proximal connector mounted on each tubing is connected by way of the six insulated wire conductors to six spaced apart sleeve electrodes mounted on each wire assembly at a distal end portion thereof. A portion of each core wire in the distal end portion of one of the wire assemblies can be caused to assume a desired configuration after distal end portions of the wire assembly are moved from a retracted position within the catheter to a position where the distal end portions are extended from the catheter and where the core wires can be caused to assume the desired configuration to form an elliptical envelope. In the retracted position, the wire assemblies are parallel and closely spaced apart thereby allowing the catheter to be inserted into an artery or a vein to place the distal end portions of the wire assemblies in a cardiac chamber where they can be extended to create the elliptical envelope. The distal end portions of the wire assemblies can then be incrementally rotated while electrical potentials are measured and recorded at different points along the surface of an endocardial wall of a cavity of the heart, such as a ventricle, that come into contact with the sleeve electrodes. Such a probe thus necessitates that the elliptical end portion thereof be rotated to measure a sufficient amount of points along the inner wall of the chamber. Such a rotation prevents a recording of all of the electrical potentials simultaneously in a single heartbeat. The shape of the elliptical envelope depending only on the central core wire contained in each one of the wire assemblies does not adapt itself to slightly different shapes and volumes of the cardiac chamber being studied. Such discrepancies in the shape and the volume of the cavity will impede the proper contact of all the sleeve electrodes with the endocardium. Also, the amount of recording sites and the distribution thereof are limited. It is noted that the above probe is non invasive, meaning that the manipulation of this catheter does not require the opening of the rib cage. Therefore, the previous disadvantages are quite acceptable for a non invasive probe.
Electrode balloons were then developed in order to be able to record electrical potentials simultaneously on the whole surface of the cardiac chamber being studied. Such electrode balloons are used in the operating room and are thus considered invasive.
The first type of ball-type balloons are used on humans in the operating room to record a plurality of endocardial electrograms simultaneously during cardiac surgery on patients subject to aneurysmectomy and/or endocardial resection. In use, the balloon after having been inserted into a ventricle is inflated so as to bring the sensor electrodes into contact with the endocardial surface thereof. Obviously, this operation is carried out after extracorporeal circulation has been started so as to empty the heart of blood. After the beginning of tachycardia, which is induced by programmed stimulation should it not be present naturally at the time of the operation, the signals picked up by the sensor electrodes are stored and analyzed so as to determine the electrode which was activated first. The operation takes between two and five minutes.
To date, two such electrode balloons inserted by a ventriculotomy have been subject of publications. A description of these balloons follows hereinbelow.
The first balloon called the Amsterdam balloon was disclosed in the article "Endocardial Mapping by Simultaneous Recording of Endocardial Electrograms During Cardiac Surgery for Ventricular Aneurysm" by Bakker et al., JACC Vol. 2, No. 5, November 1983, pages 947-953. The Amsterdam balloon is composed of two superposed latex membranes. The inner membrane represents the tight compartment whereas the outer membrane carries the sensor electrode spherical balls.
The concept of the Amsterdam balloon exploits the latex not for its elasticity but for its plane and smooth surface which facilitates its insertion into the studied cardiac chamber. The balloon, flaccid at the beginning, is inflated after introduction until it reaches the form in which it was molded. At that format, the thick latex is just taut, and not really stretched, with the electrode distribution being regular to permit extrapolation of their anatomical localization when they are hidden. Between that format, the material is a bit flaccid and beyond that same format, it stretches irregularly in view of caprices of the latex. Consequently, this balloon cannot adjust itself in all cases to various and different cavity volumes, whereby the spreading out of the electrodes can have distortions in its regularity.
The Amsterdam balloon has to be introduced in the ventricle by way of an incision in the aneurysm. In cases where a ventriculotomy is not required, the Amsterdam balloon does not have the structural characteristics that would allow it to be positioned in the ventricle while preserving the same.
The second electrode balloon, conceived for animal experimentation on the dog, was disclosed by Fann et al. in the article "Endocardial Activation Mapping and Endocardial Pace-Mapping Using a Balloon Apparatus", Am J Cardiol, Vol. 55, 1985, pages 1076-1083. In this balloon, referred hereinafter as the Chicago balloon, a tight latex chamber is covered with a not very extensible netting that carries sensor electrode balls which are mounted in pairs on inserts for a bipolar recording. The balloon is inserted directly in the left ventricle by sliding it through a guide tube. As for the Amsterdam balloon, the Chicago balloon is therefore inserted in the ventricle by way of a ventriculotomy.
A third electrode balloon, referred to as the Toronto balloon, was disclosed by Mickleborough in the article entitled "A New Intraoperative Approach for Endocardial Mapping of Ventricular Tachycardia", J Thorac Cardiovasc Surg, Vol. 95, 1988, pages 271-274. This electrode balloon for humans was designed to be inserted in the left ventricle without having recourse to a ventriculotomy as it is insertable through the left auricle and the mitral valve of the heart. Its construction is very similar to that of the Chicago balloon except that the silver electrode balls thereof are pierced to be sewn one by one to an expendable mesh which covers a double-layered latex balloon. This fixation mode is well adapted to the restraints inherent with an insertion through the mitral valve.
The following documents disclose apparatuses for the endocardial mapping of the other cardiac chambers, that is the right ventricle and the left and right auricles.
Multielectrode endocardial probes for the left and right ventricular cavities are described by Harada et al. in the article entitled "Potential Distribution Mapping: New Method for Precise Localization of Intramural Septal Origin of Ventricular Tachycardia", Circulation Vol. 78, No. 5, Nov. 1988 (suppl. III), III-137-147. This probe is made from a foam rubber cast carrying a set of silver electrode heads. However, this probe, hereinafter referred to as the St-Louis probe, was conceived for animal experimentation wherein concessions can be made regarding the insertion and withdrawal constraints. The probe not being entirely compressible, a wider opening of the auricle as well as rougher manipulations are necessary in order to set the probe in place and to withdraw it. On the other hand, withdrawal of the probe is not a preoccupation as it is withdrawn from the heart after dissection thereof.
The above probe is the only electrophysiological probe designed for the right ventricle found to date in the scientific literature. According to the above article in which it is described, the St-Louis probe has a shape that is well adapted to the right ventricle. On the other hand, the probe is limited as indicated hereinabove to animal experimentation.
Only one multielectrode electrophysiological probe model for the auricles has been disclosed to date in the scientific literature. This probe, hereinafter referred as the Maastricht probe, is described by Allessie et al. in "Intra-Atrial Reentry as a Mechanism for Atrial Flutter Induced by Acetylcholyne and Rapid Pacing in the Dog", Circulation Vol. 70, No. 1, July 1984, Pages 123-125. It consists of two rigid casts made from a polymeric resin which are strawberry and egg-shaped respectively for the left and right auricles. Each mold comprises 480 electrodes. These probes were designed specifically for animal experimentation whereby they are introduced in the auricles by a large incision through the underlying ventricles. Such incisions are not allowed for humans when the ventricle has to be preserved. Made from a rigid material, these probes are not compressible whereby larger openings and rougher manipulations are necessary for the insertion and withdrawal thereof. Moreover, these probes do not offer any latitude regarding various size auricles. On the other hand, such a construction allows for the grafting thereto of a large density of electrodes.